Conventionally, an image forming apparatus such as an MFP is provided with a scanner section serving as an image reading apparatus and a printer section. The scanner section reads a document. The image data read by the scanner section is printed by the printer section after it is processed by an image processing section.
Further, an automatic document feeder (ADF) is arranged in the image forming apparatus. In the scanner section, there is a case in which the documents sent by the ADF are read, and a case in which the documents placed on a document placing table are read. In general, in a case of copying a large quantity of documents, the scanner section reads the documents sequentially sent by the ADF. On the other hand, in a case of copying images such as a photograph, a book and the like, the scanner section reads the documents placed on the document placing table one by one.
Further, in a case of continuously reading the documents sent by the ADF, a shading correction has been performed for each document. The shading correction is performed such that the brightness distribution in a horizontal scanning direction of the signal input to the image processing section is uniform. The shading correction is performed based on the brightness of the reflected light from a white reference board provided in the scanner section such that the brightness in the horizontal scanning direction is uniform.
Further, the scanner section is provided with a carriage. The carriage includes a light source for illuminating the document, and a mirror for guiding the light reflected by the document to an image sensor. Then, in order to perform the shading correction, the carriage is moved to the position of the white reference board so that the image sensor reads the reflected light of the white reference board.
Thus, in the past, every time reading a document, the carriage needs to be moved to the position of the white reference board so as to perform the shading correction. Therefore, there is a problem that it is not possible to speed up the reading operation of document, and a further improvement is required.